OBJECTIVE: To assess the effects of abbreviated literature searches on evidence syntheses conclusions.
STUDY DESIGN AND SETTING: We randomly selected 60 Cochrane reviews of clinical interventions and repeated literature searches using 14 abbreviated approaches (combinations of MEDLINE, Embase, CENTRAL with and without searches of reference lists). If abbreviated searches missed included studies, we recalculated meta-analyses. Cochrane authors determined whether the new evidence base would change conclusions. We assessed the noninferiority of abbreviated searches allowing for a maximum of 10% changed conclusions.
RESULTS: We conducted 840 abbreviated literature searches. Noninferiority varied based on the definition of "changed conclusion". When the reduction of the certainty of a conclusion was of concern, all abbreviated searches were inferior. Searching Embase only rendered the greatest proportion of changed conclusions (27%, 95% confidence interval [CI]: 16%-40%); combining MEDLINE, Embase, CENTRAL with searches of references lists the lowest (8%, 95% CI 3%-18%). When falsely reaching an opposite conclusion was of concern, combining one database with another or with searches of reference lists was noninferior to comprehensive searches (2%, 95% CI: 0%-9%).
CONCLUSION: If decision-makers are willing to accept less certainty and a small risk for opposite conclusions, some abbreviated searches are viable options for rapid evidence syntheses. Decisions demanding high certainty require comprehensive searches.